Distribution of rapid pyrolysis products for Hami lignite and its light residue

Naomaohu lignite (NL) from Hami, Xinjiang, was ultrasonically extracted with a mixed solvent of CS₂ and acetone (in equal volumes) to obtain the extract residue (ER). The ER was then separated based on density differences with CCl₄ to yield the corresponding light residue (NL-L). The composition and structural characteristics of the light residue were characterized by proximate, ultimate, infrared, and thermogravimetric analyses (TG-DTG). The difference in the distribution of pyrolysis products between NL and NL-L was studied with rapid pyrolysis equipment (Py-GC/MS). The results showed that solvent extraction and density difference can reduce moisture and increase volatile matter. The relative content of oxygen-containing functional groups and aromatic functional groups in NL-L is greater than that in NL. The weight loss profiles of the two samples are the same, and both reach their maximum rate of weight loss at about 440 °C. It can be inferred that the process of ultrasonic extraction and density difference has little impact on the macromolecular structure of the coal. Results from rapid pyrolysis showed that the organic compounds detected in the pyrolysis products of the two samples at 440 °C were mainly aliphatic hydrocarbons and oxygen-containing compounds. The relative content of aliphatic hydrocarbons from NL-L was 11.64%, lower than that of NL, while the content of oxygen-containing compounds was increased by 17.52%.